In the manufacture of motors and generators, coils of wire are placed in slots in laminated iron cores. These coils are held in place by wedges which are inserted over the coils in the slots. Although nonmetallic fiber reinforced wedges have been used, magnetic wedges can increase the efficiency of the motor or generator by reducing core loss, temperature, frame size, and number of slots, and increasing the starting torque. (See U.S. Pat. Nos. 1,605,112 and 1,231,588). Magnetic wedges have been made from powdered iron and epoxy resins, (see U.S. Pat. No. 3,447,009) but until now it has been difficult to achieve both good physical properties and good magnetic properties in these wedges.
Good physical properties include high flexural strength since the wedge must withstand considerable stress when it is rammed into the slot and when the motor or generator is running. Also, the deflection temperature should be high since considerable heat is generated. Good magnetic properties include high permeability and low magnetic retention. The core loss, which results from eddy currents and other causes should also be low.